1. Field of the Disclosure
The disclosure relates to an optical switch.
2. Description of the Related Art
Optical switches are used in optical transmission systems for switching paths of optical signals such as wavelength multiplexing optical signals. Such optical switches use liquid crystal on silicon (LCOS) for switching paths of optical signals (see U.S. Pat. Nos. 7,092,599 and 7,397,980). LCOS is a spatial optical modulator that is able to modulate a phase of incident light by liquid crystal to diffract it. In an optical switch using LCOS, optical switching operation is realized by diffracting an optical signal entering from a certain path by LCOS and outputting it to a specific path.
In the optical switches disclosed in U.S. Pat. Nos. 7,092,599 and 7,397,980, input ports to which optical signals are input and output ports from which optical signals are output are arranged at equal intervals along a certain direction. The input ports are arranged on optical axes of lenses. Therefore, the LCOS is configured to diffract angles of incident light beams in directions of these arrangements. An optical switch having N input ports and M output ports (where N and M are integers of 1 or greater) is called as an N×M optical switch.